Over the last thirty years it has been a goal of various government agencies to develop uses for the desert plant jojoba (Simmondsia chinensis), especially the extract produced from the jojoba seeds. Due to the jojoba plant's ability to thrive in arid climatic conditions in coarse desert soils and it's life span which can extend up to 200 years, the plant was thought to be particularly useful for developing an agricultural industry in the underutilized lands of the American southwest.
The jojoba plant produces an abundance of seeds with an average yield for a mature plant of about 12 pounds (dry weight). Jojoba seeds contain about 50% by weight of a colorless, odorless oily extract which is commonly referred to as "jojoba oil". The extract is chemically an unsaturated wax made up of non-glyceride esters having a narrow range of chemical composition. Waxes of this type are relatively rare. Another natural source for wax esters is spermaceti, a wax produced from the head of the sperm whale. As the sperm whale is an endangered species and interstate sale of its oil was banned in 1973, it is not recognized as a particularly useful source for these wax esters.
Jojoba oil is more than 97% wax esters. Each wax ester is derived from one molecule of a long-chain monoethylenic alcohol esterified with one long-chain monoethylenic fatty acid. The wax esters typically are comprised of carbon chains of 38 to 44 carbon atoms. Suprisingly, the wax ester components of jojoba oil have been found to exhibit excellent flower thinning capabilities.
Fruit thinning is an advantageous and widely practiced procedure in the fruit crop industry. Many fruit bearing plants produce an excess of blossoms in a growing season. The excess flowers, and the eventual mature fruit, result in a small average fruit size and poor fruit quality for the fruit crop. Thus, in the grape industry it is desirable to reduce the number of berries on the rachis to permit larger berry size for market purposes. Further, an excess of fruit on a fruit bearing plant can result in a heavy load on the branches of the fruit tree, which reduces the tree's vigor and may lead to greater susceptibility to disease. Fruit thinning alleviates such problems and results in better a quality fruit crop.
Generally, fruit thinning entails the removal of a percentage of fruiting flowers or the prevention of formation of a percentage of fruiting bodies for a fruit bearing plant. Either the fruit producing blossoms or the immature fruit may be removed. Removal may be accomplished mechanically wherein workers will remove the fruiting flowers at some time prior to maturation. Alternatively, chemical means may be employed wherein a chemical, either in solution or powder form, is applied to the fruit trees at some optimum point before fruit maturation, thereby reducing the fruit load per fruit plant. Fruit thinning by chemical application is generally preferred as it is less labor intensive and thus less expensive.
Various chemical compounds have been disclosed which claim suitability for use as a fruit thinning agent. For example, U.S. Pat. No. 5,242,891 discloses the use of fatty acids, their salts and esters as a fruit thinning agent. The disclosed fatty acids generally have carbon chains of between 7 to 20 atoms. Additionally, U.S. Pat. No. 5,125,959 discloses pyrazole compounds for use as fruit thinning agents and U.S. Pat. No. 4,789,398 discloses the use of cholesterol as a fruit thinning agent. None of these application disclose the high molecular weight wax esters commonly found in jojoba extract for use as a flower thinning agent.
In addition to the fruit thinning ability of the wax esters found in jojoba extract, the wax esters have been found to exhibit other desirable qualities which make them a particularly effective fruit thinning agent. For example, the wax esters of jojoba extract are generally non-toxic for predator, beneficials and honeybees. The wax esters are also rainfast after the application has dried thoroughly. Thus, the wax esters are not easily washed off into the environment and fewer applications need be made relative to non-rainfast fruit thinning agents. As a result, environmental loading is kept to a minimum, costs are lowered for growers and the wax ester fruit thinning agent is environmentally safe. Additionally, the wax esters have been found to be non-phytotoxic and indeed, promote photosynthesis and stomatal conductance.
Another advantage of jojoba wax is the low volatility of wax esters. Many of the existing horticultural oils and fruit thinning agents are generally not environmentally safe in their application because they are somewhat volatile. Thus, use of these materials is hazardous to workers applying the chemical. The wax esters used in this invention provide particular stability and are significantly less volatile than horticultural oils. Specifically, the greater degree of unsaturation and the carbon chains, which are almost twice as long as fatty acid oils, enhances stability and non-volatility.